1 files changed, 34 insertions, 24 deletions
diff --git a/crypto/src/util/date/DateTimeUtilities.cs b/crypto/src/util/date/DateTimeUtilities.cs
index 72e5123a2..3660e29c2 100644
--- a/crypto/src/util/date/DateTimeUtilities.cs
+++ b/crypto/src/util/date/DateTimeUtilities.cs
@@ -2,38 +2,48 @@ using System;
 
 namespace Org.BouncyCastle.Utilities.Date
 {
-	public class DateTimeUtilities
+	public static class DateTimeUtilities
 	{
-		public static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static readonly DateTime UnixEpoch = DateTime.UnixEpoch;
+#else
+        public static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+#endif
 
-		private DateTimeUtilities()
-		{
-		}
+        public static readonly long MaxUnixMs =
+            (DateTime.MaxValue.Ticks - UnixEpoch.Ticks) / TimeSpan.TicksPerMillisecond;
+        public static readonly long MinUnixMs = 0L;
 
-		/// <summary>
-		/// Return the number of milliseconds since the Unix epoch (1 Jan., 1970 UTC) for a given DateTime value.
-		/// </summary>
-		/// <param name="dateTime">A UTC DateTime value not before epoch.</param>
-		/// <returns>Number of whole milliseconds after epoch.</returns>
-		/// <exception cref="ArgumentException">'dateTime' is before epoch.</exception>
-		public static long DateTimeToUnixMs(
-			DateTime dateTime)
+        /// <summary>
+        /// Return the number of milliseconds since the Unix epoch (1 Jan., 1970 UTC) for a given DateTime value.
+        /// </summary>
+        /// <remarks>The DateTime value will be converted to UTC (using <see cref="DateTime.ToUniversalTime"/> before
+        /// conversion.</remarks>
+        /// <param name="dateTime">A DateTime value not before the epoch.</param>
+        /// <returns>Number of whole milliseconds after epoch.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">'dateTime' is before the epoch.</exception>
+        public static long DateTimeToUnixMs(DateTime dateTime)
 		{
-			if (dateTime.CompareTo(UnixEpoch) < 0)
-				throw new ArgumentException("DateTime value may not be before the epoch", "dateTime");
+            DateTime utc = dateTime.ToUniversalTime();
+            if (utc.CompareTo(UnixEpoch) < 0)
+				throw new ArgumentOutOfRangeException(nameof(dateTime), "DateTime value may not be before the epoch");
 
-			return (dateTime.Ticks - UnixEpoch.Ticks) / TimeSpan.TicksPerMillisecond;
+			return (utc.Ticks - UnixEpoch.Ticks) / TimeSpan.TicksPerMillisecond;
 		}
 
-		/// <summary>
-		/// Create a DateTime value from the number of milliseconds since the Unix epoch (1 Jan., 1970 UTC).
-		/// </summary>
-		/// <param name="unixMs">Number of milliseconds since the epoch.</param>
-		/// <returns>A UTC DateTime value</returns>
-		public static DateTime UnixMsToDateTime(
-			long unixMs)
+        /// <summary>
+        /// Create a UTC DateTime value from the number of milliseconds since the Unix epoch (1 Jan., 1970 UTC).
+        /// </summary>
+        /// <param name="unixMs">Number of milliseconds since the epoch.</param>
+        /// <returns>A UTC DateTime value</returns>
+        /// <exception cref="ArgumentOutOfRangeException">'unixMs' is before 'MinUnixMs' or after 'MaxUnixMs'.
+        /// </exception>
+        public static DateTime UnixMsToDateTime(long unixMs)
 		{
-			return new DateTime(unixMs * TimeSpan.TicksPerMillisecond + UnixEpoch.Ticks, DateTimeKind.Utc);
+			if (unixMs < MinUnixMs || unixMs > MaxUnixMs)
+				throw new ArgumentOutOfRangeException(nameof(unixMs));
+
+            return new DateTime(unixMs * TimeSpan.TicksPerMillisecond + UnixEpoch.Ticks, DateTimeKind.Utc);
 		}
 
 		/// <summary>